Quality assurance (QA) is a critical component of radiation oncology that ensures both effective treatment delivery and patient safety. Over the last decade, dQA is now particularly important asramatic innovations in treatment delivery technologiesy have led to increasingly sophisticated and complex treatments that are difficult to adequately verify with conventional dosimetric verification systems. Corresponding innovations in verification technologies haves lagged behind, generating a potentially dangerous imbalance where traditional verification systems lack sufficient capability to adequately verify these new treatmentsopportunity for new paradigm changing comprehensive 3D dosimetry QA systems. In this proposal we address this lack and need by developing a novel truly 3D treatment verification measurement system based on a 3D radiochromic-dosimeter (Presage) with optical CT readout. There are two specific aims: (i) to optimize two advanced prototype Presage formulations (see below), and (ii) to optimize a novel low-cost 3D optical scanner. The objective of the first aim is to optimize two advanced prototype Presage formulations, for application to remote and re-useable 3D dosimetry respectively. AIn remote dosimetry, highly stable prototype Presage formulation will be optimized that will enable remote dosimetry consisting of dosimeters are shipmentped from a central base institution to a remote institution for irradiation, and then shipped back to the base institution for readout and analysis. A post irradiation stableThis formulation formulation will improve enable the comprehensiveness of remote credentialing and/or auditing tests. The second sub-aim is to optimize aA second re- useable formulation formulation will be optimized where the post irradiation optical densitydosimeter gradually `clears' within 1-2 weeks, and the dosimeter can then be re-used. This formulation will allow economic in-house use for centers with a readout optical-CT system.Potential formulation modifications have been identified. Initial studies in cuvettes will identify successful formulations which will then be scaled up to relevant 3D dosimeter dimensions for evaluation by the DUKE optical scanner. The second aim will beis the optimization of the DUKE optical-CT scanner for commercial application in a general clinic which will be conducted by the co-PI Dr. Oldham of DUKE. Prior scanners have worked defined state-of-the-art performance, well but require expensive telecentric optical lenses, and large volumes of refractive index matching fluids, and substantial expertise, making the system impractical for the general clinic. In this aim we leverage new 3D printing techniques to solve both of these challenges through creation of a novel light- collimating solid-tank . The proposed research develops a scanning system willwhich eliminates the need for both telecentric the lenses and minimize the amount ofalmost all of refractive index matching liquid. This will be achieved by manufacturing a solid tank which both surrounds the dosimeter and collimates light into parallel ray geometry. The long-term goal is to commercialize the the Presage/Optical-CT system and meet the need for an economic but hugely capable fully 3D dosimetry system for the general clinic, capable of in-house use (with re-useable PRESAGE formulations) or for remote offsite long-distance credentialing type verification (stable PRESAGE). The Presage/Optical-CT 3D dosimetry system will be a listed FDA medical device commercially sold by Heuris Inc.